1. Field of Invention
The invention relates to a pressure-measuring glow plug for a diesel engine with a plug body for insertion into a cylinder of the diesel engine, a heating rod which is arranged in the plug body, and a pressure sensor, which is arranged under an initial tension between the heating rod and the plug body in such a way that the pressure sensor is acted upon by the pressure prevailing in the combustion chamber of the cylinder, whereby the heating rod transmits the pressure in the combustion chamber of the cylinder to the pressure sensor and in which the heating rod is arranged in the plug body so as to be displaceable in a sliding manner in the axial direction relative to the plug body, so that the pressure in the combustion chamber leads to an axial motion of the heating rod relative to the plug body, as a result of which motion the pressure sensor is acted upon by a force.
2. Description of Related Art
With a pressure-measuring or pressure gauge glow plug of the above mentioned type, the combustion pressure is transmitted directly via the heating rod to the pressure sensor, without the geometry and the strength of the plug body having an influence or being linked. All the usual functions of the glow plug are retained.
With such a pressure-measuring glow plug, sealing is preferably provided between the heating rod and the plug body. The seal is formed from a metal membrane or by an elastomer seal.
Use of metal membrane as a seal, however, has the drawback of a stiff spring characteristic and a small spring excursion, which leads to component loading. An elastomer seal, on the other hand, is temperature-sensitive.